Motor and ignition safety control system for liquid fuel burners



Nov. 23, 1954 c. H. MILLERWISE ET AL 2,695,054

MOTOR AND IGNITION SAFETY CONTROL SYSTEM UEL BURNERS FOR LIQUID F Filed Nov M K. M

MD ATTORNEY g G MN om mv w m mv/ m vm mm a M 3% w no mm mm mm 5. .55 3 ow mm 2 M m ww nu HH mm mm m vm 8 on United States Patent MOTOR AND IGNITION SAFETY CONTROL SYSTEM FOR LIQUID FUEL BURNERS Carl H. Millerwise, Detroit, and William H. Hohmeyer,

Birmingham, Mich assignors to Detroit Controls Corporation, a corporation of Michigan Application November 27, 1951, Serial No. 258,344 6 Claims. (Cl. 158-28) This invention relates to new and useful improvements in control systems for liquid fuel burners and more particularly to a primary control system which is constructed of a minimum number of control parts.

In the past, many types of control systems, devices and circuits have been proposed for controlling the operation of liquid fuel burners, but substantially all of those have involved the use of very complicated circuits involving many switches, relays, and complicated timing mechanisms. In this invention there is provided a control system having a minimum number of operating control parts to provide for maximum simplicity and efiiciency in operation.

Accordingly, it is one object of this invention to provide a new and improved control circuit for liquid fuel burners.

Another object is to provide a control circuit for liquid fuel burners having as few control switches and as simple a timing mechanism as possible.

Another object is to provide a liquid fuel burner control system which will turn 011 a burner motor and ignition, after a predetermined time turn off the ignition, and if no flame occurs in the burner by the time the ignition is turned off, will, after a predetermined further period of time, turn off the burner motor, all with a minimum number of control switches and circuits.

Another object is to provide a liquid fuel burner control circuit and control devices therefor which are simply and inexpensively constructed and assembled.

Other objects will become apparent from time to time throughout the specification and claims as hereinafter related.

This invention comprises the new and improved construction and combination of parts and their operating relationship each to each, which will be described more fully hereinafter and the novelty of which will be particularly pointed out and distinctly claimed.

In the accompanying drawing, to be taken as part of this specification, there is clearly and fully illustrated a preferred embodiment of this invention, in which drawing the figure shows in more or less diagrammatical form a control system for liquid fuel burners which is the subject of this invention.

Referring to the drawing by characters of reference there is disclosed a liquid fuel burner 1 having a burner motor 2 and an electric spark ignition 3. The control circuit for the burner 1 comprises a transformer 4 having a: primary 5 connected to a high voltage power source 6 and a secondary 7 for supplying low voltage to a portion of the control system. it should be noted that the terms high and low voltage so used herein refer to voltages on the order of v. and 624 v. respectively. From one side of the transformer primary 5 a wire 8 is connected to a contact arm 9 of a switch 10 comprising contact arms 9 and 11 and switch contacts 12 and 13. The contact arm 11 of the switch 10 which is biased against a stop 14 is connected by wires 15 and 16 to one side of the burner motor 2 and by wires 15 and 17 to the contact arm 18 of an initially closed switch 19. The switch 19 comprises movable contact arms 18 and 20 having switch contacts 21 and 22 which are biased toward engagement with each other. The switch contact arm 2% is connected by wire 23 to the primary 24 of ignition transformer 25. The ignition transformer 25 has a secondary coil 26 connected by wires 27 and 28 to the spark ignition 3. The ignition transformer primary 24 is connected as at 29 to a return wire 30 from the burner motor 2 which is in turn connected to the contact arm 31 of an initially closed switch 32. The switch 32 comprises contact arms 31 and 33 which carry switch contacts 34 and 35, respectively, biased into initial engagement. The contact arm 33 of the switch 32 is connected back to the high voltage power source 6 by a return wire 36. A suitable snap acting mechanism 37 cooperates with the switch contact arm 33 to snap open the contacts of the switch 32 upon predetermined movement thereof in one direction. The snap mechanism 37 may be any suitable snap mechanism, but it is illustrated diagrammatically as an overcenter spring 38 and adjustment screw 39 therefor. The adjustment screw 39 is operable to vary the relation of the spring 38 to the contact arm 33. The compressive force of spring 38 biases the contact arm 33 into engagement with the contact arm 31. A reset button 40 is provided in overlying relation to the switch contact arm 33 for resetting the same from a snapped open position. The contact arms 11, 20 and 31 are interconnected for movement together by suitable thrust transmitting rods or members 41 and 42. The switch 19 has a stop 43 positioned to engage the contact arm 18 for opening the contacts thereof. There is provided a timing means 44 for operating the switches 10, 19 and 32 in suitable sequence which comprises a bi-metallic heat motor formed by a warpable bi-metal member 45 heated by a resistance heater 46 of predetermined size.

The bi-metal member 45 actuates the switches through a thrust 47, and through the interconnectiong thrust members 41 and 42. The bi-metal member 45 warps at a rate which is determined by the rate of heat input from the heater 46 and the force against which the bimetal member Works. Since the heating of the bimetal by the resistance heater 46 is a function of the time that the heater was energized, it is apparent that the timing operation of the heat motor may be adjusted by varying either the distance through which the bimetal must move or the force against which it must work. The screw 39 is operable to adjust the compressive force exerted by the spring 38 and thus varies the timing operation by varying the force against which the bi-metal must work. If the compression of spring 38 is increased the bi-metal must warp with a greater force, which requires a longer heating period. Similarly the spring 38 could be adjusted relative to the arm 39 to vary the snap point and thus vary the distance which the arm 33 must move before snapping over center. One side of the resistance heater 46 is connected by a wire 48 to one side of the transformer secondary 7. The other side of the resistance heater 46 is connected by wires 49, 50 and 51 to the fixed contacts 52 and 53 of a single-pole, double-throw switch 54. A resistor 55 is interposed in circuit between the wires 49 and 51 for a purpose which Will be described hereinafter. The movable pole 56 of the switch 54 carries movable contacts 57 and 58 cooperable with the fixed contacts 52 and 53, respectively, and is connected by a wire 59 to the fixed contact 60 of a room thermostat 61. The movable pole 56 of the switch 54 is operated by a suitable flame responsive means such as a bi-metal helix 62 positioned in the burner stack 63 for response to flame temperature. The room thermostat 61 is positioned for response to the output of heat to the space being heated by the burner 1 and has a suitable thermostatic means such as a bi-metal 64 connected by a wire 65 to the other side of the transformer secondary 7 and carries a movable contact 66 cooperable with the fixed contact 60.

Operation 48, resistance heater 46, wire 49, wire '50, contacts 52 3. and 57 of switch 54,,wire 59, contacts 60 and 66 of the thermostat 61, thermostat blade 64, and wire 65, completing the connection to the transformer secondary 7. With. this circuit completed, the heat output. of: the heater 46 will. cause the bi-metall 45 tomove at a rate dependent upon. the heat output of. the heater 46, the type of bi-rnetallused in the member 45, and the resistance against which the hi-metal member 45 must operate. As the bi-metal. member 45' is moved upwards, it. moves the thrust member 47 against. the contact arm. 9 and thus-moves the switch contact. 12 into engagement with. contact 13. When the contacts 12 and 13' are brought. into engagement, a high. voltage circuit iscompleted from the power source 6 by way of wire 8,- contact blade 9, contacts 12 and 13, and contact blade 11 to wire- 15. After wire 15 the circuit divides and part is connected through the ignition. and. part through the burner motor. The circuit through the burner motor extends from wire 15' by'way of. wire 16. The circuit through the ignition extends from. wire 15 by way of wire: 17,- contact blade 18} initially closed contacts 21 and 22, contact blade 20,- and Wire 23 tothe ignition transformer primary 24'. The burner and ignition circuits join. again at point- 29 onv Wire 35) which connects to contact-arm 31- of the switch 3:2. The circuit is completed back to. the other side of the high voltage power source through contact arm 3-1, closed contacts Maud-35, contactv arm 33 and' wire 36'. At this stage of the operation, with all three switches closed, both the burner motor and' ignition are energized and inthe normal course of operation flame should occur in the burner. After, the predetermined time (deter mined bythe physical: constantsof the heater 46 and bi -metal45), the contact arms 18 and 29 of the switch 1-9 will be moved until the contact arm 18 engages the stop 43, and upon further movement. the contacts 21 and 22 are separated, thus breaking the circuit to the ignition transformer 24. If at this point no flame has occurred in the burner, the-bi-rnetal member 45 of the timer 44 will continue to move; and after predetermined further movement. the contact arms. 31 and 33 of the switch 32 will be movedtoan. overcenter position relative to the snap mechanism 37 and: the contact arm 33 and switch contact 35 will move away from the contact. 34 with. a snap movement, thus breaking the circuit to both the burner motor 2 and ignition transformer 24, If flame occurs in the burner 1- after the closing of the switch contacts 12 and 1-3' of switch 10 and prior to the opening of contacts 21' and 22 of switch 19, the flame responsive bi-metal. 62 will move the contact pole 56 of. the doublethrow switch 54 and open the contacts 52 and 57 and close the contacts 53- and'58 to place the resistor 55 'n series circuit with the resistance heater 46 for the bi-metal member 45. When the resistor 55 is placed in series withv the resistance heater 46,-the voltage drop through the resistor 46 is reduced to a point such that the heat output thereof to the bi-metal member 45 is sufficient to maintain the same in. an actuated position between the point at which the contacts 2i and 22 of. switch 19 are opened and the point at which the switch 32 is snapped open. It will be seen that innormal. operation when thesystem is required to produce heat, the timing means first causes the switches to be] placed in: a. positionv toenergize both the. ignition and-burner motor. After apredetermined time-the ignition switch is opened and the burner motor circuit remains. on. If. flamehas occurred in the burner by this time, the timer mechanism will hold. the switches in this position. Upon de-energization, the ignition switch will first close and. then the switch 10 controlling. both. the burner and ignition will reopen. The closing. of. the ignition switch just prior to de-energization of the system will cause a momentary ignition at this time and will consume any residual combustible: gases left in the burner. On the-other hand, if flame does not occur in theburner by the time the ignition switch is opened, the timer mechanism moves the switch 32 until the same is snapped open, as previously described, and the burner and ignition are bothv shut down by that operation. After the switch 32 has been snapped open, it is necessary that the contact arm 33 and contact 35' be reset manu-v ally from this safety position and the reset button 41.5.1 provided for that purpose. It should also be noted that. the snap mechanism 37 includes an adjustment means such as the screw 39 for the overcenter'spring and a flame responsive double .place said resistor in. said series relation in response to 38 to vary its relation to the contact arm 33 and thus vary the time required to move to a safety snapped open position.

From the foregoing description of the system disclosed herein, it is seen that there is here provided a very simple control system for a liquid fuel burner having a very simple timing mechanism and having considerably less than the usual number of control switches and other control parts therefor.

While there hasbeen described herein only one form of this invention, it-will be obvious to those skilled in the art that other modifications of this system are pos sible without departing from the scope and intent of this invention as defined in the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent of the United States is:

1. In a burner control system, a liquid fuel burner, a burner motor and-electriccircuit therefor, an electric ignition means and circuit therefor; switch. means comprising a pair of. switches, one of which has contacts in said ignition circuit, and the other of which has contacts in both said ignition and said motor circuits; electro-the'rmal" timing; means having aresistance heater and electric circuit therefor, associated with said switch means for actuation thereof; said timing means being operable after a predetermined period of energization to actuate said switch means to energize said motor and ignition circuits, after a predetermined further period of energization to open said one ignition switch, and after a still further predetermined period of energization. to open said other switch; a thermostatic switch responsive to the temperature of the space heated by said burner and controlling energization of said timing means, an electric resistor'arranged to be in series circuit with said resistance heater to reduce the energy output to said timing means to a point of actuation whereat said ignition switch is opened. and said other switch remains closed, and a flame responsive switch arranged to place said resistor in said series relation in response to the occurrence of flame in said burner prior to the opening of said other switch.

2. In a burner control system, a liquid fuel burner, a burner motor and electric circuit therefor, an electric ignition means and circuit therefor; switch means comprising a pair of switches, one of which has contacts in said ignition circuit, and the other of. which has contacts in both said ignition and said motor circuits; electrothermal timing means having a resistance heater and electric circuit therefor, associated with said switch means for actuation thereof; said timing means being operable after a predetermined period of energization to actuate said switch means to energize said motor and ignition circuits, after a predetermined further period of energization to open said one ignition switch, and after a still further predetermined period of energization to open said other switch; a thermostatic switch responsive to the temperature of the space heated by said burner and controlling energization of said timing means, an electric resistor initially out of circuit out arranged for connection in series circuit withsaid rcsistance heater to reduce the" energy output to said timing means to apoint of actuation where'at said ignition switch is opened and said other switch remains closed, throw switch, arranged to the occurrence of flame in said burner prior to the open ing of said other switch. 7

3. In a burner. control system, a liquid fuel burner, a burner motor and electric circuit therefor, an electric ignition means and circuit therefor, a switch having initially closed contacts in said ignition circuit, switch means including initially open contacts in both said ignition and said motor circuits, said switch means including a switch contact arm and a snap mechanism therefor operable upon predetermined movement in one direction to snap open and break said motor and said ignition circuits, electrohermal timing means having a resistance heater, a circuit for said resistance heater for re versibly actuating said timing means, said timing means being arranged to actuate said switch and said. switch means in said one direction upon energization. and in the other direction upon deenergization; said timing means being operable upon energization to actuate said switch means to energize said motor and ignition cira cuits, and after a predetermined time to open said ignition controlling switch, and to actuate said switch and switch means in reverse sequence upon deenergization; said timing means also being operable upon a predetermined further period of energization to actuate said switch means through said predetermined movement to cause the same to snap open, a thermostatic switch rcsponsive to the temperature of the space heated by said burner and controlling energization of said timing means heater circuit, an electric resistor initially out of circuit but arranged to be in series circuit with said resistance heater, said resistor being operable to reduce the heat output to said timing means to a point of actuation intermediate the opening of said ignition controlling switch and said snap opening movement, and a double throw switch and flame responsive operating means therefor arranged to place said resistor in said series relation in response to the occurrence of flame in said burner.

4. In a burner control system, a liquid fuel burner, a burner motor and electric circuit therefor, an electric ignition means and circuit therefor, said ignition and motor circuits being connected in parallel and having common portions, a first switch having initially closed switch having stop means cooperable with one contact arm of said first switch to cause the same to be opened by movement of the other contact arm thereof through a movement less than said predetermined movement, electric timing means comprising a bimetallic heat motor and resistmeans being arranged to actuate said switches sequentially in said one direction upon energization so that said second switch is closed first, and said first switch opened after a predetermined time, and in reverse sequence upon de energization; said timing means being operable after a further predetermined period of energization to move said third switch to said snap opening position, a thermostatic switch responsive to the temperature of the space heated by said burner to control energization of said resistance heater circuit, a double throw switch, parallel circuits connecting said resistance heater to the fixed contacts of said double throw switch, the movable pole of said double throw switch being connected to said thermostatic switch, a resistor in one of said parallel circuits operable to reduce the heat output of said resistance heater to a point such that said heat motor cannot move sufficiently to snap open said third switch, and means responsive to the occurrence of flame in said burner to actuate said double throw switch to connect said resistor in series with said resistance heater.

5. A burner control system as defined in claim 4 including a movable reset member cooperable with said third switch contact arm for resetting the same from said snapped open position.

6. A burner control system as defined in claim 4 including means to adjust said snap mechanism to vary the time of energization of said timing means required to snap open said third switch.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,674,051 McCabe June 19, 1928 1,876,281 Eiseman Sept. 6, 1932 2,012,322 Satchwell Aug. 27, 1935 2,135,829 McGoldrick Nov. 8, 1938 2,170,426 Raney Aug. 22, 1939 2,261,586 McGrath Nov. 4, 1941 2,593,518 Aubert Apr. 22, 1952 

